Automotive exhaust gases contain contaminants such as unburned hydrocarbons (HCs), NOx gases, and SOx gases. An attempt to reduce these contaminants has hitherto been made, for example, by a method in which, for SOx, S in gasoline is removed, or unburned HCs are burned in the presence of a catalyst.
Specifically, as shown in FIG. 17, in an automotive system 100, air is introduced through an automatic element (filter) 102, is then passed through an air flow rate sensor 104, and is fed into an engine 106. On the other hand, a gasoline within a fuel tank 108 is fed through a fuel pump 110 into the engine 106.
Further, the automotive system 100 is constructed so that, based on the results of detection with an A/F sensor 112, fuel injection in the engine 106 is controlled by a fuel injection control device 114 so that the air-fuel ratio is brought to a predetermined theoretical air-fuel ratio.
An exhaust gas from the engine 106 is fed into a catalyst device 116 where hydrocarbons (HCs) contained in the exhaust gas are burned. The exhaust gas is then passed through an oxygen concentration sensor 118 and is discharged as an exhaust gas.